1. Field of the Invention
This invention relates to a novel vehicle headlamp. More specifically, the invention relates to a vehicle headlamp having a discharge bulb-lighting device mounted on an outer surface of a body, and more particularly to the art of positively waterproofing that portion of the body on which the discharge bulb-lighting device is mounted.
2. Description of the Related Art
In a vehicle headlamp in which a discharge bulb-lighting device for lighting a discharge bulb within a body is mounted on an outer surface of the body, an opening for the passage of power supply cords (for connection between the discharge bulb and the discharge bulb-lighting device) therethrough need to be formed in the body. Therefore, it is necessary to waterproof the region between the opening and the discharge bulb-lighting device.
There has been proposed a vehicle headlamp in which the waterproof effect is achieved with a structure shown in FIG. 8.
More specifically, an opening b is formed through a bottom wall of a body a within which a discharge bulb (not shown) is provided. A downwardly-open fitting groove c is formed on a lower surface of the body a at a peripheral edge portion of the opening b over an entire periphery thereof. A packing d is fitted in the fitting groove c. A plurality of screw-fixing bosses e are formed around the fitting groove c.
A plurality of screw-fixing piece portions g are formed on and project from a peripheral surface of a discharge bulb-lighting device f. A fitting rib h is formed on that side (face) of this discharge bulb-lighting device, facing the bottom surface of the body a, in opposed relation to the fitting groove c.
The discharge bulb-lighting device f is located so that a distal end of the fitting rib h is abutted against the packing d provided in the fitting groove c of the body a. In this condition, tapping screws i, passing respectively through the screw-fixing piece portions g from the lower side; are threaded respectively into bottom holes (not shown) formed respectively in the screw-fixing bosses e, thereby fixedly mounting the discharge bulb-lighting device on the body a.
Then, power supply cords j are connected to a discharge bulb (not shown).
In the above vehicle headlamp, the fitting rib h, formed on the discharge bulb-lighting device f, is abutted against the packing d fitted in the fitting groove c, thereby forming a waterproof seal at the area of contact between the packing d and the fitting rib h.
Therefore, that portion of the packing d, against which the fitting rib h is abutted, is much more deformed than the other portion thereof. Therefore, the packing d is subjected to permanent deformation to degrade the waterproofing performance.
The discharge bulb-lighting device f is secured to the body a by threading the tapping screws i respectively into the bottom holes formed respectively in the screw-fixing bosses e. If the direction of application of a threading torque to the tapping screw i deviates perpendicularly from the proper threading direction, the direction of treading of the tapping screw i is deflected. This causes the position of mounting of the discharge bulb-lighting device f to deviate from its proper mounting position. When such a deviation occurs, the distal end of the fitting rib h, while squeezing the packing d, deviates in the direction of the width of the fitting groove c, so that the deformation of the packing d becomes more remarkable and uneven. This adversely affects the waterproof performance.
Under the above circumstances, in the vehicle headlamp shown in FIG. 8, the portion of the body a where the discharge bulb-lighting device f is mounted may not be waterproofed reliably.
An object of this invention is to provide a vehicle headlamp, having a discharge bulb-lighting device that is waterproof.
A vehicle headlamp of the present invention has an opening formed in a body within which a discharge bulb is provided. A discharge bulb-lighting device is mounted on the body to cover the opening. The discharge bulb and the discharge bulb-lighting device are connected together by a power supply cord via the opening. The waterproof wall of a cylindrical shape is formed on and projects from that portion of the body disposed near a peripheral edge of the opening. A positioning rib is formed on and projects from that portion of the body disposed in surrounding relation to an outer surface of the waterproof wall. A waterproof rib of a cylindrical shape, which is smaller in diameter than the waterproof wall, is formed on the discharge bulb-lighting device. A restraint portion for contacting with an inner surface of the positioning rib is formed on the discharge bulb-lighting device. The discharge bulb-lighting device is fastened by screws to the body, with an O-ring held between the waterproof rib and the waterproof wall and also with the restraint portion held in contact with the inner surface of the positioning rib.
Therefore, in the vehicle headlamp of the present invention, that portion of the body, on which the discharge bulb-lighting device is mounted, is positively waterproofed. Namely, the O-ring is uniformly compressed between the waterproof wall of the body and the waterproof rib of the discharge bulb-lighting device and, therefore, is deformed uniformly over an entire periphery thereof. Its elastic fatigue is smaller than where the O-ring undergoes a large deformation at a localized portion thereof. Therefore, the O-ring can maintain the waterproofing function for a long period of time.
Furthermore, at the time of fastening the discharge bulb-lighting device to the body by the screws, even if a rotating torque is applied to each screw so that a moment, acting in other direction than the threading direction, is added to cause the discharge bulb-lighting device to have a tendency to deviate in a direction perpendicular to the threading direction, the discharge bulb-lighting device is accurately mounted in the intended mounting position. This is because the restraint portion of the discharge bulb-lighting device is restrained from being displaced by the positioning rib of the body. Therefore, the O-ring will not be unevenly deformed and can maintain the waterproofing function for a long period of time.